Problems existing in traditional envelope technology include for example, bandwidth of envelope signal being proportional to bandwidth of input signal, and the bandwidth of the envelope signal being more than twice the bandwidth of the input signal. When the bandwidth of the input signal is broad, the bandwidth of the envelope signal needs to be wider, and this causes loss of efficiency for a wireless communication system. If the transmission path of the input signal and transmission path of the envelope signal are different, such difference can cause time misalignments, which could lead to other problems (e.g., signal distortion).